40 Wound Care Canada Volume 18, Number 3 · Fall 2020

Feeding the Foot: Nutrition and Diabetic Foot UlcersBy Ellen Mackay, MSc RD CDE

Diabetic foot ulcers (DFUs) are a serious complication of diabetes that can impair quality of life and lead to fur-ther problems such as infection and possibly lower extremity amputations.

Globally, DFUs occur in 15% of those with dia-betes and are seen more often in men and those with type 2 diabetes.1 Other risk factors for DFUs include longer duration of diabetes, age, higher body-mass index (BMI) and tobacco use.

Individuals with diabetes are particularly vulner-able to foot ulceration due to the circulatory and neurological changes associated with the disease. These changes to blood vessels and peripheral nerves can result in loss of protective sensation and poor nutrient delivery to the extremities, lead-ing to an increased risk of injury and poor healing.

Daily inspection of feet, annual foot exams, proper footwear and a healthy lifestyle are at the core of diabetes self-management education to prevent or identify early changes to the feet and efficiently treat ulcers if they occur. See Wounds Canada’s comprehensive document Caring for Your Feet: Safe Foot Care If You Have Diabetes, a patient-focused tool clinicians can use with patients.

Nutrition, however, is largely overlooked as part of the prevention and treatment of DFUs, despite the pivotal role it plays in the management of diabetes and prevention of diabetes-related complications.2-3 Nutritional intake can impact

immune function, blood glucose levels, blood pressure, cholesterol, body weight and wound healing.4 Wound healing alone is dependent upon adequate nutrition intake, and research shows that malnutrition may have a significant impact on limb-preservation outcomes for limb-threaten-ing DFUs.5 Nutrition support is a low-risk, cost-ef-fective measure to prevent or treat DFUs and should be considered in all patients with diabetes.

To date, there are no evidence-based nutrition guidelines for the treatment and prevention of DFUs. It is unknown if the recently released evi-dence-based international guidelines for the pre-vention and treatment of pressure injuries can be extrapolated to DFUs.6 In the absence of nutrition guidelines specifically for DFUs, however, these updated pressure injury guidelines should be con-sidered when determining nutrition requirements for wound healing. (See Nutrition and Pressure Injury Healing: Updated Recommendations for a review of these guidelines.7)

But diabetic foot ulcers are a different wound from a pressure injury and may have different nutrition considerations. The question remains: Are there specific nutrient concerns for individuals with diabetes at risk for, or with, a DFU? There is increas-ing awareness that a person living with diabetes will face significant nutritional challenges that, if overcome, could ultimately prevent the develop-ment of a DFU or improve the chances that the ulcer will heal in a timely manner.8-9 The remainder

Volume 18, Number 3 · Fall 2020 Wound Care Canada 41

of this article will focus on key nutritional areas to consider in the prevention and treatment of a DFU. Table 1 outlines the nutrition checklist for use in supporting a person with a DFU.

Malnutrition ScreeningWound healing is an anabolic process that increases the nutritional needs for energy, pro-tein, fluid and some micronutrients. Malnutrition

Table 1: Nutrition Checklist for DFU

Malnutrition Use a validated malnutrition screening tool.

Glycemic Control Target < 7% for most individuals with diabetes.• Adjust or titrate diabetes medications.• Encourage low glycemic food choices. • Spread carbohydrates evenly through the day.• Encourage enhanced blood glucose monitoring.

Nutrition Recommendations

Provide adequate nutrition and hydration for wound healing while maintaining euglycemia.• Energy: 30–35 kcal/d• Protein: 1.25–1.5 g/kg• Fluid: 30 ml/kg (adjust for extra losses)

Key Micronutrients• Vitamin D• B12 (especially

with long-term metformin use)

• Iron• Vitamin C• Zinc

• Correct deficiencies.• Offer general multivitamin/mineral supplement if intake is poor.• Supplement at physiological doses.

Patient-driven Care • Adapt diet for cultural and personal preferences.• Address chewing/swallowing safety.• Enhance eating environment.• Provide nutrition education to prevent malnutrition and enhance intake.

42 Wound Care Canada Volume 18, Number 3 · Fall 2020

can have a negative impact on wound healing. Some patients with diabetes may be at higher risk of malnutrition due to long-term restrict-ed diets, poor access to adequate nutrition and drug–nutrient interaction. Some studies have shown a high rate of malnutrition in patients with diabetes.1,8,10

Not only have DFUs been shown to be associ-ated with malnutrition, but nutrition status has been correlated with the severity of the ulcer, risk of infection and poor outcomes, such as amputa-tion.1,5 And as nutrition status worsens, the severity of DFUs (as measured by the Wagner ulcer classifi-cation system) and risk of infection increases. The wound itself may have a negative impact on nutri-tion status due to high nutrient demand for healing and loss of nutrients from wound exudate.11

For this reason, all patients with a DFU should be screened for malnutrition using a validated screening tool. The Mini Nutritional Assessment is a valid tool in treating diabetes.5 Treating or pre-venting malnutrition repletes nutrition stores and ultimately improves wound healing. Nutritional assessment also addresses the underlying causes of malnutrition and supports a long-term nutri-tion care plan to prevent future episodes of mal-nutrition. For a further review of malnutrition and wound healing, see Malnutrition in Wound Care.12

Glycemic ControlLong-term elevated glucose can alter

circulation and innervation that increases the risk of a DFU,

along with other complica-tions such as blindness,

cardiovascular disease and renal impairment.

Hyperglycemia con-tributes to blood vessel rigidity that impacts blood flow—resulting in poor oxygen and nutrient delivery to the wound bed.13 In addition, hyper-

glycemia may impair the inflamma-tory process, interrupting the wound healing cascade and leading to delayed wound heal-ing.14-16 Elevated A1c has been associated with slower healing rates of foot ulcers.17

The primary goal of diabetes manage-ment is to maintain glucose levels at target, often measured by glycated hemoglobin (A1c). The A1c reflects the average blood glucose over a two- to three-month window.2 While there is no specific A1c target to promote healing, the pri-mary goal of preventing microvascular and neur-opathic damage is supported by targeting an A1c below 7%.2 For those at risk for hypoglycemia, targets may be set higher.

Healthy Eating: Focus on CarbohydratesA well-balanced diet that incorporates pro-tein, carbohydrates and fat is the cornerstone of healthy eating for diabetes management. In diabetes, the focus is often on restricting or controlling carbohydrate intake. The challenge for patients is to support the elevated nutri-tion needs for wound healing and skin integrity while maintaining blood glucose levels at target. Insufficient carbohydrates during wound healing may result in protein being oxidized for energy and contribute to poor healing, muscle wasting and malnutrition. Carbohydrates contribute to energy needs, and the minimum recommended intake is no less than 130 grams per day for those over 18 years of age.18 Food sources of carbohy-drate (grains and starches, fruit, milk products) also provide valuable micronutrients that support wound healing.

Helping patients understand how food affects blood glucose is key to glycemic control. Basic nutrition education should include a review of the food sources of carbohydrates in the diet.

Volume 18, Number 3 · Fall 2020 Wound Care Canada 43

Diabetes Canada’s

Beyond the Basics Meal

Planning Guide is one tool that

teaches patients which foods have

carbohydrates and how to practise portion control.

Patients should be encouraged to distribute carbohydrates throughout the

day and include plenty of higher fibre foods and non-carbohydrate vegetables. Incorporating edu-cation on glycemic index shows patients how food impacts blood glucose. Oral hypoglycemic agents and/or insulin dose should be considered to assist patients in reaching their glycemic targets.

By reading food labels, patients can find out the available carbohydrate content of a food. (Available carbohydrate is the total carbohydrate content less the fibre content, in grams.) For those with the desire for more detailed nutrition education or those taking insulin or on pump therapy, learning carbohydrate counting and matching insulin (if taking) to food choices will assist in managing glucose levels.

Through blood glucose testing at home with a glucometer, flash or continuous glucose monitor, patients learn the effect of food and activity on glucose levels. Supporting patients in minimizing glucose excursions and recognizing and respond-ing to their glucose patterns will prevent micro- and macrovascular changes.

Protein: The Necessary Ingredient for Healing WoundsProtein is vital throughout the wound healing cascade, as it is required for the synthesis of enzymes and the creation of collagen, connective tissue, capillaries and epithelial cells. Amino acids provide the building blocks of antibodies, macro-phages and a healthy immune system. A lack of protein may prolong the inflammatory stage of wound healing, impair adequate collagen syntheses—leading to reduced tensile strength

of a closed wound—and increase the risk of a wound becoming chronic. Recommended intakes of protein that support wound healing are 1.25 to 1.5 g/kg.6 Protein requirements need to be adjusted in patients with certain comorbidities, such as renal or liver disease.

Protein-rich foods include meat, poultry, fish, eggs, milk products and legumes. Ensuring that protein is eaten at all meals fuels the require-ments for tissue growth. Protein also slows stomach emptying and may lower the glycemic response when consumed with a carbohy-drate-rich food.

Arginine, Glutamine and Beta-hydroxy-beta-methylbutyrate (HMB)Recent interest in specific amino acids and pro-tein supplementation in diabetes is emerging.

Arginine and glutamine are two conditionally essential amino acids; our body naturally pro-duces arginine and glutamine, but in times of stress, such as with a wound or sepsis, the body’s demand for these amino acids outweighs sup-ply, and they become conditionally essential and must be provided through the diet. These amino acids play an important role in repairing wounds, enhancing immune function, stimulating insulin secretion, promoting the transport of amino acids into tissue cells and supporting the synthesis of protein and collagen in the cells. Arginine is also a precursor to nitric oxide, a neurotransmit-ter that causes blood vessels to relax and dilate, improving blood flow to the wound bed. B-hydroxy B-methylbutyrate (HMB) is a metabolite of leucine and may enhance muscle protein synthesis.

For these reasons, there has been inter-est in using arginine, glutamine and HMB supplementation for patients with DFUs. Research suggests this type of supplement may

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have value in the healing of DFUs, particularly in a subset of study subjects, including those with poor limb perfusion or low serum albumin lev-els.1,8 Further research into this area is warranted. To date, however, these enhanced nutritional for-mulas are not available in Canada.

CaloriesRecommended energy intake for wound healing is estimated at 30 to 35 kcal/kg/day.6 In patients with elevated BMI > 30, energy requirements may be tapered to 20 to 25 kcal/kg/day.

FatFat provides a source of calories that ensures suf-ficient energy intake with minimal effect on gly-cemia and provides essential fat-soluble vitamins. Monounsaturated fats and omega-3 polyunsatur-ated fats are often referred to as “healthy fats,” as they have positive effects on a patient’s lipid pro-file and cardiovascular outcomes.2 Omega-3 fats may play an additional role in DFUs due to their anti-inflammatory and antioxidant effects.19 Some research has shown enhanced ulcer healing with supplementation,20 but further research is needed in this area.

Clinicians should encourage patients to choose olive and canola oil, and avocados, and to include nuts and seeds, in small portions, to ensure suf-ficient calorie and omega-3 intake. Omega-3 fats can be found in fatty fish (salmon, artic char, mackerel, trout, herring and light tuna), seeds (flax, hemp) and nuts.

Vitamins and MineralsSeveral key micronutrients are involved in preserving skin integrity and wound healing. See Table 2 for a review of key nutrients and their function in wound healing. Note that general mal-nutrition screening may not be sensitive enough to detect micronutrition deficiencies.3 While diabetes itself may not directly impact nutrition requirements, there is evidence of an association between DFUs and certain deficiencies.3,21–22 Studies show that micronutrient deficiencies, including in vitamin C, zinc, iron and vitamin D, are common in those with DFUs.3,22–23

Clinicians should also consider drug–nutrient interactions. Metformin, often the first-line treat-ment for type 2 diabetes, will affect the absorp-tion of B12 and has been associated with B12 deficiency. While not directly associated with wound healing, a B12 deficiency will have an impact on anemia, and it may present as periph-eral neuropathy.24

Despite the association of micronutrient defi-ciencies and DFUs, there is limited evidence that supplementation will enhance ulcer healing or indications as to optimal intake levels to target.

Volume 18, Number 3 · Fall 2020 Wound Care Canada 45

This is largely due to the paucity of large RCTs and the variety of ways in which researchers have measured outcomes.4,11

Adding Supplements?At present there is insufficient evidence to sup-port vitamin and mineral supplementation at lev-els above the daily recommended intake (DRI) for people with a DFU, unless a deficiency is suspect-ed or confirmed. However, individuals with a DFU may not be able to consume an optimal diet and may have additional vitamin and mineral needs. These patients may benefit from a general daily multivitamin and mineral supplement to fill the nutrition gaps.4 Supplementation without consid-ering adequate energy, protein and hydration will do little to improve wound healing.

Clinicians should assess oral intake before con-sidering additional micronutrient supplementa-tion. Reviewing nutritional intake from all sources,

including current multivitamin/mineral supple-ments, oral nutrition supplements and fortified foods, ensures that over-supplementation or excessive intake does not occur. It is not uncom-mon for some patients to receive multiple sources of micronutrients with possible nutrient inter-actions (for example, long-term excess zinc intake may impact copper metabolism).13

ConclusionHealthy eating can impact glycemic control, wound healing and ultimately limb preservation. Those at risk for a DFU should receive foot care education on early warning signs and manage-ment of complications. In addition, all individuals at risk for a DFU should be screened for malnutri-tion and assessed by a registered dietitian with expertise in diabetes management. Patients may be at risk for some nutrition deficiencies, and nutrition therapy offers a low-risk, cost-effective

Table 2: Key Micronutrients and Their Functions in Wound Healing3,13,21,25

Micronutrient Function in Wound Healing DRI (Adults)

Vitamin C • Neutrophil migration• Fibroblast proliferation• Collagen formation• Immunity• Promotes iron absorption

• 75 mg/d women• 90 mg/d men

Vitamin A • Stimulates immune system• Maintains mucosal and epithelial integrity• Collagen formation

• 700 mcg RAE women • 900 mcg RAE men

Vitamin D • Possible role in glycemic control • Immune function• Reduces inflammation

• 600 IU• 800 IU > 70 years

Copper • Necessary for connective tissue and collagen synthesis• Red blood cell formation

• 900 μg/day

Iron • Necessary for collagen synthesis and strength• T cell and phagocyte function• Needed for hemoglobin formation and oxygen transportation

• 8 mg/d

Zinc • Synthesis of granulation tissue• Re-epithelialization• Anti-inflammatory and antimicrobial effects• Cell division, protein synthesis, collagen deposition

• 8 mg/d women• 11 mg/d men

RAE: Retinol Activity EquivalentsDRI: Dietary Reference Intakes 

46 Wound Care Canada Volume 18, Number 3 · Fall 2020

way to support prevention and treatment of DFUs and to optimize wound healing.

By providing nutrition support, clinicians can also address the underlying cause of the deficien-cy or malnutrition and play a complementary role in helping patients prevent diabetes-related com-plications. Informed food choices, especially with regard to foods containing carbohydrates, can impact overall glycemic control while promoting adequate intake to support wound healing.

References1. Zhang SS, Tang ZY, Fang P, Qian HJ, Xu L, Ning G. Nutritional

status deteriorates as the severity of diabetic foot ulcers increase and independently associates with prognosis. Exp Ther Med. 2013;5(1):215–222.

2. Sievenpiper JL, Chan CB, Dworatzek PD, Freeze C, Williams SL. Diabetes Canada 2018 clinical practice guidelines for the prevention and management of diabetes in Canada: Nutrition therapy. Can J Diabetes. 2018;42(Suppl 1): S64–S79.

3. Brookes JDL, Jaya JS, Tran H, Vaska A, Werner-Gibbings K, D’Mello AC, et al. Broad-ranging nutritional deficiencies predict amputation in diabetic foot ulcers. Int J Low Extrem Wounds. 2020;19(1):27–33.

4. Collins C. Diabetic foot ulcers and nutrition: Making the connection. Today’s Wound Clinic. 2019;13(7):10-15.

5. Gau BR, Chen HY, Hung SY, Yang HM, Yeh JT, Huang CH, et al. The impact of nutritional status on treatment outcomes of patients with limb-threatening diabetic foot ulcers. J Diabetes Complications. 2016;30(1):138–142.

6. European Pressure Ulcer Advisory Panel, National Pressure Injury Advisory Panel and Pan Pacific Pressure Injury Alliance. Prevention and Treatment of Pressure Ulcers/Injuries: Clinical Practice Guidelines. The International Guidelines. Emily Haesler, editor. EPUAP/NPIAP/PPPIA; 2019.

7. Mackay E. Nutrition and pressure injury healing: Updated recommendations. Wound Care Canada. 2020;18(1):20–26.

8. Armstrong DG, Hanft JR, Driver VR, Smith APS, Lazaro-Martinez JL, Reyselman AM, et al. Effect of oral nutritional supplementation on wound healing in diabetic foot ulcers: A prospective randomized controlled trial. Diabet Med. 2014;31(9):1069–77.

9. Vas PRJ, Edmonds ME, Papanas N. Nutritional supplementation for the diabetic foot ulcer: The big challenge. Int J Low Extrem Wounds. 2017;16(4):226–229.

10. Eneroth M, Larsson J, Oscarsson C, Apelqvist J. Nutritional supplementation for diabetic foot ulcers: The first RCT. J Wound Care. 2004;13:230–234.

11. Moore ZEH, Corcoran MA, Pattonet D. Nutritional interventions for treating food ulcers in people with diabetes. Cochrane Database Syst Rev. 2020;7:1465–1858.

12. Mackay E. Malnutrition in wound care. Wound Care Canada. 2019;17(3):32–36.

13. Collins N, Sloan C. Diabetic wound healing through nutrition and glycemic control. Today’s Wound Clinic. 2013;7(2).

14. Maier H, Ilich JZ, Kim J, Spicer MT. Nutrition supplementation for diabetic wound healing: A systematic review of current literature. SKINmed. 2013;11(4):217–225.

15. Khan MN. The influence of diabetes on wound healing. The Diabetic Foot. 2005;8(3):144+.

16. Botros M, Kuhnke J, Embil J, Goettl K, Morin C, Parsons L, et al. Best practice recommendations for the prevention and management of diabetic foot ulcers. In: Foundations of Best Practice for Skin and Wound Management. A supplement of Wound Care Canada; 2017.

17. Christman AL, Selvin E, Margolis DJ, Lazarus GS, Garza LA. Hemoglobin A1C is a predictor of healing rates in diabetic wounds. J Invest Dermatol. 2011;131(10):2121–2127.

18. Food and Nutrition Board, Institute of Medicine of the National Academics. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids. Washington: The National Academies Press; 2005. Retrieved from: www.nal.usda.gov/sites/default/files/fnic_uploads//energy_full_report.pdf.

19. Li K, Huang T, Zheng J, Wu K, Li D. Effect of marine-derived n-3 polyunsaturated fatty acids on C-reactive protein, interleukin 6 and tumor necrosis factor alpha: A meta-analysis. PLOS One. 2014;9(2):e88103.

20. Soleimani Z, Hashemdokht F, Bahmani F, Taghizadeh M, Memarzadeh MR, Asemi Z. Clinical and metabolic response to flaxseed oil omega-3 fatty acids supplementation in patients with diabetic foot ulcer: A randomized, double-blind, placebo-controlled trial. J Diabetes Complications. 2017;31(9):1394–1400.

21. Kulprachakarm K, Ounjaijean S, Wungrath J, Mani R, Rerkasem K. Micronutrients and natural compounds status and their effects on wound healing in the diabetic foot ulcer. Int J Lower Extrem Wounds. 2017;16(4):244–250.

22. Pena G, Kuang B, Cowled P, Howell S, Dawson J, Philpot R, et al. Micronutrient status in diabetic patients with foot ulcers. Adv Wound Care. 2019;9(1):9–15.

23. Razzaghi R, Pourbagheri H, Momen-Heravi M, Bahmani F, Shadi J, Soleimani Z, et al. The effects of vitamin D supplementation on wound healing and metabolic status in patients with diabetic foot ulcers: A randomized, double-blind, placebo-controlled trial. J Diabetes Complications. 2017;31(4):766–772.

24. Aroda VR, Edelstein SL, Goldberg RB, Knowler WC, Marcovina SM, Orchard TJ, et al. Long-term metformin use and vitamin B12 deficiency in the Diabetes Prevention Program Outcomes Study. J Clin Endocrinol Metab. 2016;101(4):1754–1761.

25. Munoz N, Posthauer ME, Cereda E, Schols JMGA, Haesleret E. The Role of Nutrition for Pressure Injury Prevention and Healing: The 2019 International Clinical Practice Guideline Recommendations. Adv Skin Wound. 2020;33(3):123–126.

Volume 18, Number 3 · Fall 2020 Wound Care Canada 47

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